The semiconductor laser module is generally used as a light source of the signals and as an excitation light source of the optical fiber amplifier and the like in the optical communications.
FIG. 12 are figures showing the semiconductor laser module (100), FIG. 12A is a top view, and FIG. 12B is a side view. The semiconductor laser module (100) mainly comprises a semiconductor laser element (101), an optical fiber (102), a base (103) and so forth. The semiconductor laser element (101) is fixed onto the base (103). The optical fiber (102) is arranged on the base (103) and is fixed by means of an anchoring material (104), so as to be optically coupled with the emitted light from the semiconductor laser element (101). As the anchoring material (104), synthetic resin adhesives, solder, low melting glass or the like can be used.
In alignment/fixation of the optical fiber (102) to the semiconductor laser element (101), a passive aligning method or an active alignment method can be used. In recent years, for the semiconductor laser module used in the high speed communication at 10 Gb/s or more, the active alignment with which more precise adjustment can be made is mainly used. This active alignment is carried out as follows: the light-incident-side end of the optical fiber (102) is positioned so that it is optically coupled with the emitted light from the semiconductor laser element (101), and the laser light is monitored with a detector at the other end in this situation.
When the optical fiber (102) is fixed, the anchoring material (104), such as solder or low melting glass, is heated and melted by heating means such as a soldering iron, a laser or the like. The optical fiber (102) can be freely moved within the anchoring material (104) in the molten state. The position of the optical fiber (102) is adjusted by monitoring the value of the detected signal. When the detected signal has reached a sufficient value, the anchoring material (104) is cooled and the optical fiber (102) is fixed to a definite position.
FIG. 13A shows a situation in which a solder preform is heated with the laser light. As a conventional fixing method of the optical fiber (102), solder is used as the anchoring material (104) to fix the optical fiber (102), for example, as shown in FIG. 13A. As shown in FIG. 13A, the anchoring material (104), which is a solder preform, is arranged on the base (103), and is heated by irradiation of the laser light (105) emitted from a laser light irradiator (not shown) from above the anchoring material (104). The anchoring material (104) is heated and melted, and then the optical fiber (102) is fixed onto the base (103).
Since the material constructing the base (103) is generally constituted of CuW or the like which has high thermal conductivity, when the base is heated for a long time, the heat may propagate to other optical elements and may affect them adversely. For this reason, it is necessary to melt and fix the anchoring material (104) (the solder) with short-time heating. However, this approach will give a problem that the base member cannot be sufficiently heated within a time when the anchoring material (104) (the solder) is melted, and thus wetting between the anchoring material (104) (the solder) and the base (103) may become insufficient.
Another fixing method of the optical fiber is, for example, a method to heat the anchoring material such as a solder preform, low melting glass and the like with a heating wire, soft beam (light from a lamp such as a halogen lamp or the like, for example), a semiconductor laser, a YAG laser or the like (refer to Patent document 1 and Patent document 3, for example).
FIG. 13B shows a situation in which the anchoring material is heated by a heating element. As shown in FIG. 13B, a heating wire (111) is wound up around the lower part of the supporting element (112) for fixing the anchoring material (104) (the solder) thereon. When the optical fiber (102) is aligned and fixed, electric current is flown through the heating wire (111) and the temperature of the supporting element (112) itself is raised. The anchoring material (104) (the solder) is melted by the supporting element (112), and then the optical fiber (102) is fixed onto the supporting element (112).
There is a method for fixing the optical fiber, in which the optical fiber supporting element is made of an electric resistor, wherein the solder (the anchoring material) is heated with the resistor (refer to Patent document 2 and Patent document 4, for example).
FIG. 14A shows how the anchoring material is heated by a resistor. As shown in FIG. 14B, the resistor (122) is arranged on a substrate (121) and side pads (123) are provided on both ends of the resistor (122). The substrate (121) on which the side pads (123) and the resistor (122) are connected, is installed on the base (103). The optical fiber (102) is arranged on the resistor (122), and the anchoring material (104) (the solder) is provided thereon.
When electric current is applied to the side pads (123) provided on both ends of the resistor (122), the resistor (122) will generate heat. Thus, the anchoring material (104) (the solder) is melted. Then supply of the electric current is stopped, and the optical fiber (102) is fixed onto the resistor (122).